A new method for determining the concentration of atmospheric alcohols using the nitrite formation reaction

A new method for measuring the concentration of atmospheric alcohols was de veloped and applied to ambient air samples. In the method, air samples were collected in 200 mi Pyrex glass bottles whose surface had been cleaned and treated with a chromic acid mixture. Alcohols in the sample were allowed t o react in the dark with intentionally added nitrogen dioxide (200 ppm by v olume (ppmv) concentration level) on the glass surface to yield correspondi ng alkyl nitrites. The concentration of the nitrite thus yielded is determi ned separately by gas chromatography (GC) with an electron capture detector (ECD). Alcohol concentration in the sample is calculated using a calibrate d conversion factor of each alcohol to its nitrite. Detection limits for me thanol, ethanol, and isopropanol are 0.9, 0.7, and 1.8 ppbv (parts per bill ion by volume), respectively, using 500 mu l injection of the reaction mixt ure by this method. In order to examine the feasibility of this method for an ambient air sample, several measurements were done. Air samples were tak en on a road with heavy traffic near the campus of Osaka Prefecture Univers ity. Concentration levels of methanol, ethanol, and isopropanol were 4-10, 3-25, and 1.5-20 ppbv, respectively. Diurnal variation of these alcohols' c oncentration was also measured. Generally, alcohol concentrations were high er in the evening than those in the daytime, increasing up to the levels of 10-20, 10-25, and 10-20 ppbv for methanol, ethanol, and isopropanol, respe ctively. (C) 1999 Elsevier Science B.V. All rights reserved.